1. Field of the Invention
The invention relates to a hybrid vehicle, a controller for a hybrid vehicle, and a control method for a hybrid vehicle and, more particularly, to a hybrid vehicle including an internal combustion engine.
2. Description of Related Art
Generally, there is known a variable valve actuating device for changing the operation characteristic of an intake valve of an internal combustion engine. There is a variable valve actuating device configured to be able to change at least one of the valve lift or valve operating angle of an intake valve (see, for example, Japanese Patent Application Publication No. 2009-202662 (JP 2009-202662 A), Japanese Patent Application Publication No. 2004-183610 (JP 2004-183610 A), Japanese Patent Application Publication No. 2013-53610 (JP 2013-53610 A), Japanese Patent Application Publication No. 2008-25550 (JP 2008-25550 A), Japanese Patent Application Publication No. 2012-117376 (JP 2012-117376 A) and Japanese Patent Application Publication No. 9-242519 (JP 9-242519 A)). It is possible to change the operating characteristic of the internal combustion engine with the variable valve actuating device.
For example, JP 2009-202662 A describes a hybrid vehicle including a variable valve actuating device. In this hybrid vehicle, when the variable, valve actuating device is diagnosed a failure, stop of an internal combustion engine is prohibited, and a motor-assisted drive mode is executed. In the motor-assisted drive mode, the hybrid vehicle travels by using power of both the internal combustion engine and a motor. As a result, it is possible to ensure traveling performance while avoiding a start-up failure of the internal combustion engine.
There is known a hybrid vehicle that travels while switching between modes (see, for example, Japanese Patent Application Publication No. 2013-129380 (JP 2013-129380 A) and International Application Publication No. 2012/131941). The modes include a charge depleting (CD) mode and a charge sustaining (CS) mode. In the CD mode, the state of charge (SOC) of an electrical storage device is consumed. In the CS mode, the SOC is kept. In this hybrid vehicle, the CD mode is selected until the SOC decreases to a predetermined level, and then the CS mode is selected.